Controlling the passage of light is desirable in a variety of settings. For example, articles such as windows or sunglasses are desirably made in a manner allowing blockage or passage of light, controllably, to provide a desired amount of shade from sunlight. Optical displays are constructed and arranged to produce, or allow passage of, light in a predetermined, recognizable pattern, symbol, or series of symbols, for example in the form of written text, an advertisement or other sign. A variety of other systems are known for use in modulation, sensing, and recording using light.
Some known optical control systems or sensors use flexible components and/or fluids. U.S. Pat. No. 3,641,354 (De Ment) describes a system for optical modulation for use with optical computers, data processing, and optical information processing systems that includes a container, having at least one flexible wall, into which and out of which a liquid or gas can be pumped. One or more flexible walls of the container can be made convex or concave depending upon the fluid pressure within the container relative to fluid pressure outside of the container, or can be altered in configuration in other ways to focus, reflect, or otherwise alter light from a laser or incoherent light source.
U.S. Pat. No. 4,382,657 (Lemaitre) provides astronomical mirrors or aspherical gratings defined by a thin disk, having a reflecting surface, and a cylindrical ring on a support that is essentially parallel to and supports the disk, the system forming a cavity defined on one side by the disk. Control of the pressure of a fluid within the cavity, relative to pressure outside of the system, causes elastic flexion of the disk to create a concave or convex lens.
U.S. Pat. No. 4,274,706 (Tangonan) describes a flexible, reflective diffraction grating, for example made from a sheet of grooved, acetate plastic film including a reflective aluminum coating, positioned at a convexly-curved end of a waveguide. Light introduced through an input/output surface at an opposite end of the waveguide propagates to the curved end at which the grating is positioned, and light is diffracted by the grating and focused by the curved end back into the input/output end of the waveguide. The system can act as a coupler for wavelength multiplexing or demultiplexing of multimode optical signals in optical circuits.
U.S. Pat. No. 3,716,359 (Sheridon) describes the use of elastomers in various imaging systems for cyclic recording, storage, and erasure of optical information. One system involves a transparent substrate, optionally including an optically reflective surface, a conductive layer on the substrate, a photoconductive layer on the conductive layer, and an elastomer layer on the photoconductive layer. The system makes use of the properties of elastomeric imaging devices in which frost images, screened frost images, and limited spatial frequency or holographic images can be produced. A corona discharge can be used to charge, in a selective manner, a surface of the elastomer and optionally the substrate thereby creating an electrical field across the photoconductor and elastomer combination. Where the photoconductor is exposed to light, the electric field is altered resulting in a mechanical force that deforms the elastomer. Sheridon states that the system can be used for large panel displays.
U.S. Pat. No. 4,897,325 (Akkapeddi) describes a flexible mask for use in photolithography. The flexible mask is made by providing a flexible substrate such as 20-50 mil thick glass, a metallic layer on the glass, and a photoresist layer on the metallic layer, patterning the photoresist layer via known techniques, and developing the mask by selectively removing portions of the metal film resulting in a pattern of metal film on the flexible glass film. The flexible mask can be made to conform to a nonplanar structure including a layer of photoresist on a nonplanar surface, and irradiation through the mask, followed by development, can result in a pattern of photoresist on the nonplanar surface which can be followed by additional development resulting in an ultimate desired patterned, nonplanar surface.
International Pat. Publication WO 96/29629 (Whitesides, et al.) describes encapsulation of a liquid metal within a cavity of a flexible material such as an elastomer. Where the interior surface of the cavity is complementary to a diffraction grating surface, the liquid metal can define a flexible diffraction grating. The interior surface can be of another optically-interesting shape, such as a convex or concave shape, to form a liquid metal into a desired optical surface.
Liquid crystals are well-known for use in displays. In typical liquid crystal display systems, a liquid crystalline material is provided in a chamber across which an electric field can be applied. Plane-polarized light is directed at the liquid crystalline material and, when the material is made to align with the plane-polarized light, via application of an electric field, the light passes through the material. Where an electric field is not applied the liquid crystalline material does not align with the plane of the polarized light, and light passage is blocked. These and other types of liquid crystalline systems find widespread use as displays.
The above and other disclosures are representative of advancements in certain fields of optical modulation. It is an object of the invention to provide a new class of relatively inexpensive and non-complex optical modulation systems.